High Surface Area Fiber and Method of Construction Thereof

ABSTRACT

A high surface area fiber and method of construction thereof is provided. The high surface area fiber includes an inner fiber extending along a longitudinal central axis. The inner fiber has a plurality of legs extending lengthwise in generally parallel relation with one another and with the central axis. Each of the legs extends radially away from the central axis to a first peak. First channels are formed between adjacent legs in generally parallel relation with one another and with the central axis. At least some of the legs have protrusions extending laterally outwardly therefrom. The protrusions extend lengthwise in generally parallel relation with one another and with the central axis.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 61/877,727, filed Sep. 13, 2013, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to fibers having a high surface areaand to their method of construction.

2. Related Art

Traditionally, round fibers are used in the textile art. Thecross-sectional shape of a round fiber is circular. As such, roundfibers have an outer surface area of that is minimal, defined by(3.14)×(fiber diameter)×(fiber length), and the two ways to increase thesurface area of a given length of a round fiber is to increase itsdiameter, thereby resulting in the fiber occupying a larger amount ofspace and having an increased weight, or by using many small roundfibers to increase the surface area while using the same amount ofweight. This is where nanofibers or electrospun technology has itsbenefits. The smaller the fibers the more surface area there is in agiven volume, which in turn gives more filtration effect. In manyapplications, space and weight are tightly controlled, thereby requiringuse of a fiber with the highest surface area possible.

Non-round fibers having an increased surface area relative to roundfibers are known. Such fibers have multiple lengthwise extending legs,with each leg extending radially outwardly from a central axis of thefiber to form lengthwise extending channels on the surface of the fiber.Although the known legs provide an increased surface area to the fiber,lending to improving the filtration, sound and fluid absorbency andcapillary action, further improvements in accordance with the inventionprovide significant increases in the surface area of fibers, therebyfurther enhancing their filtration, sound and fluid absorbencycharacteristics.

Small diameter fibers are commonly made with the “islands in the sea”design. This is where many small fibers made up of one material areextruded within another sacrificial material, so that once the outersacrificial material is washed away, what remains are many smallindividual diameter fibers. This allows the encapsulated plurality offibers to be stretched when cooled while still maintaining their innershape, but allowing for smaller diameter, individual fibers to be made.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a high surface areafiber is provided. The high surface area fiber includes an inner fiberextending along a longitudinal central axis. The inner fiber has aplurality of legs extending lengthwise in generally parallel relationwith one another and with the central axis. Each of the legs extendsradially away from the central axis to a first peak. First channels areformed between adjacent legs. The first channels extend in generallyparallel relation with one another and with the central axis. At leastsome of the legs have protrusions extending laterally outwardlytherefrom. The protrusions extend lengthwise in generally parallelrelation with one another and with the central axis.

In accordance with a further aspect of the invention, each leg hasopposite first sides, wherein each of the opposite first sides having aplurality of the protrusions extending laterally outwardly therefrom.

In accordance with a further aspect of the invention, the opposite sidesof each leg converge toward their respective peak.

In accordance with a further aspect of the invention, each protrusionextends to a second peak, wherein each of the protrusions has oppositesecond sides converging toward their respective second peak.

In accordance with a further aspect of the invention, the inner fiber isformed from a first material extending coincident with the central axis,and an outer sheath, separate from the inner fiber, is formed from asecond material that encapsulates the first material, wherein the firstand second materials are different.

In accordance with a further aspect of the invention, the secondmaterial is dissolvable in a solvent.

In accordance with a further aspect of the invention, the secondmaterial can be provided to dissolve in water.

In accordance with a further aspect of the invention, a method ofconstructing a high surface area fiber is provided. The method includesextruding an inner fiber having a longitudinal central axis and aplurality of legs extending lengthwise in generally parallel relationwith one another and with the central axis, with each of the legsextending radially away from the central axis to a first peak to formfirst channels between adjacent legs, wherein the first channels extendin generally parallel relation with one another and with the centralaxis. The method further includes extruding protrusions simultaneouslywith the legs, with the protrusions extending laterally outwardly fromat least some of the legs and extending lengthwise in generally parallelrelation with one another and with the central axis to form secondchannels between adjacent protrusions. The method further includesco-extruding an outer sheath about the inner fiber from a secondmaterial that is different from the first material, such that the outersheath at least partially fills the first and second channels.

In accordance with a further aspect of the invention, the method furtherincludes extruding each leg having opposite first sides, and extruding aplurality of the protrusions extending outwardly from each of theopposite first sides.

In accordance with a further aspect of the invention, the method furtherincludes extruding the opposite sides of each leg converging toward thepeak.

In accordance with a further aspect of the invention, the method furtherincludes extruding each protrusion extending to a second peak, andextruding each of the protrusions having opposite second sidesconverging toward the second peak.

In accordance with a further aspect of the invention, the method furtherincludes providing the second material as being dissolvable in asolvent.

In accordance with a further aspect of the invention, the method canfurther include providing the second material as being dissolvable inwater.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of the presentinvention will become more readily appreciated when considered inconnection with the following detailed description of presentlypreferred embodiments and best mode, appended claims and accompanyingdrawings, in which:

FIG. 1 is a perspective view of a high surface area fiber constructed inaccordance with one embodiment of the invention;

FIG. 2A is a cross-sectional view taken generally along the line 2-2 ofFIG. 1;

FIG. 2B is a view similar to FIG. 2A with an outer sheath of theextruded fiber having been dissolved away;

FIG. 3A is a cross-sectional similar to FIG. 2A of a fiber constructedin accordance with another embodiment of the invention;

FIG. 3B is a view similar to FIG. 3A with an outer sheath of theextruded fiber having been dissolved away;

FIG. 4 is an enlarged partial view of the fiber of FIG. 2B;

FIG. 5 is an enlarged partial view of the fiber of FIG. 3B; and

FIG. 6 is a partial perspective view of a plurality of high surfaceareas fibers constructed in accordance with another aspect of theinvention shown coextruded within a sacrificial sheath.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

Referring in more detail to the drawings, FIG. 1 illustrates a highsurface area filament, and referred to hereafter as fiber 10,constructed in accordance with the invention. The fiber 10 can be formedhaving any suitable continuous length and diameter, as desired. Thefiber 10 includes a continuous inner fiber 11 that extends lengthwisealong a longitudinal central axis 12. The inner fiber 11 has a pluralityof legs 14 extending lengthwise in generally parallel relation with oneanother and with the central axis 12. Each of the legs 14 extendradially outwardly in branched fashion away from a central body 16 ofthe inner fiber 11, and thus, away from the central axis 12 to a firstpeak 18. With the legs 14 extending in parallel relation with oneanother, a plurality of continuous first channels 20 are formed by thelegs 14, wherein each of the channels 20 is formed as a continuousvalley between adjacent legs 14. As such, the first channels 20 extendin generally parallel relation with one another and also with thecentral axis 12. At least some of the legs 14, and shown here as each ofthe legs 14, have elongate ridges and also referred to as lobes, ridges,fingers, protrusions or arms 22, extending laterally outwardlytherefrom. Each of the arms 22 extends radially outwardly to a secondpeak 24. The arms 22 extend lengthwise continuously in generallyparallel relation with one another and with the central axis 12, andthus, continuous second channels 26 are formed between adjacent arms 22.The lengthwise extending legs 14 and arms 22 of the inner fiber 11provide the inner fiber 11 with an increased surface area, as comparedto a cylindrical monofilament, which in turn enhances the ability of thefiber 10 to filter and absorb sound and/or fluid when woven, knit,braided, or otherwise formed into a fabric. Accordingly, a textilefabric formed with the fibers 10, whether the fibers 10 are interlacedvia weaving, knitting, or braiding, also referred to as interlaced yarnsor filaments, or whether the fabric is formed as a nonwoven material,having a web formed at least in part including small fibers 10, is ableto function with an increased capacity to filter and/or absorbparticulate, sound, and fluid.

The fiber 10 is initially formed as a bi-component co-extrusion, withthe inner fiber 11 being extruded from a first material having thegeometric features described above extruded coincident with the centralaxis 12, and with an outer sheath 28 being simultaneously extruded,referred hereafter as coextruded, from a second material about the firstmaterial. The outer sheath 28 can fully encapsulate or partiallyencapsulate the inner fiber 11 to either completely fill or at leastpartially fill the first and second channels 20, 26, wherein the firstand second materials are different types of material. The first materialcan be extruded from a standard thermoplastic resinous material, such aspolypropylene, polyester, nylon, polyethylene, thermoplastic urethanes,co-polyesters, or liquid crystalline polymers, by way of example andwithout limitation. The second material is extruded from a sacrificial,dissolvable resinous thermoplastic, such as, but not limited to,polyactide (PLA), co-polyester (PETG), polyvinyl alcohol (PVA),ethylene-vinyl alcohol copolymer (EVOH), or a water-solublethermoplastic polymer resin. As such, upon extruding the bicomponentfiber 10, and allowing the extruded fiber 10 to solidify, the outersheath 28 can be readily dissolved, when desired, including immediatelythereafter, or after forming the desired end product, such as a textilematerial, whether woven, knit, braided, or a nonwoven. Accordingly, thefiber 10 can first be processed as a generally standard monofilamenthaving a generally circular cross-section, or otherwise, including agenerally oval or flatted cross-section, and then after forming the endproduct, the outer sheath 28 can be dissolved to exposed theencapsulated inner fiber 11. As such, processing the inner fiber 11 intothe textile fabric can be made easy, as with a standard monofilament,and thereafter, the more complex shape of the inner fiber 11 can beexposed by dissolving the outer sheath 28 away from the inner fiber 11.To dissolve the outer sheath 28, any suitable solvent can be used,depending on the material content of the second material, such as NaOH,acids, or in the case of a water-soluble polymer such as Exceval, watercan be used to dissolve the outer sheath 28.

As shown in FIG. 6, to improve manufacturing efficiencies, a pluralityof the fibers 10 can be coextruded within a single sacrificial outersheath 28, whereupon dissolving the outer sheath 28, the plurality ofindividual fibers 10 are exposed for individual use.

The central body 16 of the inner fiber 11 can be formed having anydesired cross-sectional geometry, including round, oval, or otherwise.The legs 14 extend radially outwardly from the central body 16 along theentire length of the central body 16 and have opposite sides, referredto hereafter as first sides 30. The opposite first sides 30 of each leg14 converge toward the first peak 18. Each of the opposite first sides30 have at least one, and shown as a plurality of the arms 22 extendinglaterally outwardly therefrom. Each arm 22 extends along the entirelength of the leg 14 from which it extends, and each arm 22 has oppositesides, referred to hereafter as second sides 32, converging toward thesecond peak 24. Accordingly, the surface area of each leg 14, ascompared to a leg not having arms extending outwardly therefrom, isincreased by the additional surface area provided by the sides 32 ofeach arm 22 extending outwardly therefrom. It should be recognized thatthe legs 14 and arms 22 can be configured having any desired shape orcontour, such as shown in FIGS. 2A, 2B, wherein the legs 14 aregenerally serpentine or zig-zag shaped, as a result of the sinuouspattern of the arms 22 extending outwardly therefrom, and also as shownin FIGS. 3A, 3B, wherein the legs 14 are generally triangular in shapeand the arms 22 extend outwardly from the opposite sides 30 in generallyminor relation with one another. It should also be recognized that thenumber of legs 14, arms 22 and associated first and second channels 20,26 can be provided as desired, and further, that legs 14, arms 22 andassociated first and second channels 20, 26 are nano-sized in width andheight, such as between about 200-1000 nanometers, depending on theapplication.

Many modifications and variations of the present invention are possiblein light of the above teachings. It is, therefore, to be understood thatthe invention may be practiced otherwise than as specifically described,and that the scope of the invention is defined by any ultimately allowedclaims.

What is claimed is:
 1. A high surface area fiber, comprising: anelongate inner fiber extending along a longitudinal central axis, saidinner fiber having a plurality of elongate legs extending lengthwise ingenerally parallel relation with one another and with said central axis,each of said legs extending radially outwardly from said central axis toa first peak, said legs being spaced circumferentially from one anotherby first channels extending between adjacent legs, at least some of saidlegs having protrusions extending laterally outwardly therefrom, each ofsaid protrusions extending to a second peak, said protrusions beingspaced from one another by second channels extending between adjacentprotrusions; and an outer sheath at least partially filling said firstand second channels.
 2. The high surface area fiber of claim 1 whereinsaid protrusions extend lengthwise in generally parallel relation withone another and with said central axis.
 3. The high surface area fiberof claim 1 wherein each leg has opposite first sides, each of saidopposite first sides having a plurality of said protrusions extendingoutwardly therefrom.
 4. The high surface area fiber of claim 3 whereinsaid opposite sides of each leg converge toward said first peak.
 5. Thehigh surface area fiber of claim 4 wherein each protrusion has oppositesecond sides converging toward said second peak.
 6. The high surfacearea fiber of claim 1 wherein said inner fiber is formed from a firstmaterial extending coincident with said central axis said outer sheathis formed from a second material, said first and second materials beingdifferent.
 7. The high surface area fiber of claim 6 wherein said secondmaterial is water soluble.
 8. A method of constructing a high surfacearea fiber, comprising: extruding an inner fiber from a first material,the inner fiber extending along a longitudinal central axis with aplurality of legs extending lengthwise along the inner fiber ingenerally parallel relation with one another and with the central axis,each of the legs extending radially outwardly from the central axis to afirst peak with first channels being formed between adjacent legs, atleast some of the legs having protrusions extending laterally outwardlytherefrom, each of the protrusions extending to a second peak withsecond channels being formed between adjacent protrusions; and extrudingan outer sheath about the inner fiber, the outer sheath being formedfrom a second material that is different from the first material,wherein the outer sheath at least partially fills the first and secondchannels.
 9. The method of claim 8 further including extruding each leghaving opposite first sides, and extruding a plurality of theprotrusions extending outwardly from each of the opposite first sides.10. The method of claim 9 further including extruding the opposite sidesof each leg converging toward the first peak.
 11. The method of claim 10further including extruding each protrusion having opposite second sidesconverging toward the second peak.